Electronic devices, including mobile computing and/or communication devices, are becoming smaller thereby driving the weight and size of data storage devices down, while requiring large storage capacity in the terabyte range and low power consumption. An increasing storage capacity would require the need for increased precision in tracking the movement of the read/write head.
Data storage devices, for example hard disk drives (HDDs), employ servo systems for tracking and controlling the movement of the read/write head.
In a conventional hard disk drive having a rotating magnetic media, there is only one magnetic layer to record data. Servo systems, e.g., as shown in FIG. 1A, employ embedded servo where the servo information runs radially across the tracks 110 from the inner diameter (ID) to the outer diameter (OD) of the disc 100 in a series of “servo wedges” 120 interspersed with data 130. Therefore, the servo information is only detected when the read/write head moves over these servo wedges 120. In between the servo wedges, no servo information is received by the head.
Data storage devices also employ dedicated servo, e.g. as shown in FIG. 1B, where the servo information is provided on a servo layer 150 distinct from the data recording layer 160. In other words, a magnetic disk may include two magnetic layers, wherein the servo layer 150 is used to record servo patterns, and the data recording layer 160 is used to record user data.
Furthermore, in conventional hard disk drives and similar data storage devices, the head either reads or writes, but cannot perform both operations simultaneously.